diff --git a/backend/src/MoShiro.Backend.Application/Query/QueryService.cs b/backend/src/MoShiro.Backend.Application/Query/QueryService.cs
index c97921f..8bb0b7b 100644
--- a/backend/src/MoShiro.Backend.Application/Query/QueryService.cs
+++ b/backend/src/MoShiro.Backend.Application/Query/QueryService.cs
@@ -23,9 +23,11 @@ public sealed class QueryService
     private readonly ITestStore _tests;
     private readonly BackendOptions _options;
     private readonly TimeProvider _time;
+    private readonly AgentRuntime _runtime;
 
-    public QueryService(RangeResolver resolver, SourcePlanner planner, RowLoader loader, HotLayer hot, IEventStore events, ITestStore tests, BackendOptions options, TimeProvider time)
+    public QueryService(RangeResolver resolver, SourcePlanner planner, RowLoader loader, HotLayer hot, IEventStore events, ITestStore tests, BackendOptions options, TimeProvider time, AgentRuntime runtime)
     {
+        _runtime = runtime;
         _resolver = resolver;
         _planner = planner;
         _loader = loader;
@@ -56,11 +58,16 @@ public sealed class QueryService
 
     // ───────────────────────── 单条线路的时序 ─────────────────────────
 
+    /// <summary>这条线路现在是不是连着（Agent 报告了这个 Probe 的会话）：连着的线路窗口以当前时间为终点，不去查“最后一个样本”——Backend 刚重启、热层和持久层还没追上时，后者会落后好几个小时，页面就显示成旧数据。</summary>
+    private bool IsConnected(LineKey line) =>
+        _runtime.TryGet(line.Agent, out AgentRuntimeState? state) && state.Probes.Any(p => p.Id == line.Probe.Value && p.IpVersion == line.IpVersion);
+
     public async ValueTask<Result<SeriesResult>> SeriesAsync(LineKey line, RangeRequest request, MetricSelection selection, CancellationToken ct)
     {
         // anchor=latest：离线或刚恢复的线路，窗口以它最后一个样本为终点（落在最近 5 秒之内就当作在线，仍以当前时间为终点）
         if (string.Equals(request.Anchor, "latest", StringComparison.OrdinalIgnoreCase) && request.To is null && request.From is null && request.Range is not null
-            && RangeResolver.TryParseSpan(request.Range, out long span))
+            && RangeResolver.TryParseSpan(request.Range, out long span)
+            && !IsConnected(line))
         {
             long now = _time.GetUtcNow().ToUnixTimeMilliseconds();
             if (await _loader.LatestSampleMsAsync(line.Agent, line.Series, now, ct) is { } latest && latest < now - 5000)